What was the fatal flaw that caused the Space Shuttle Challenger disaster?


What was the fatal flaw that caused the Space Shuttle Challenger disaster?

In: 695

The so called “O” ring on the solid rocket boosters failed. They sealed the sections of the solid rocket boosters.

The failure came from the cold temperatures the night before the launch. This was a known possibility. The sealing material lost its integrity below some temperature, and needed to be above that threshold for a certain time to recover. Engineers were calling for the launch to be scrubbed to avoid the possibility of the failure. They were called into a meeting and forced to OK the launch or resign. They reluctantly agreed. (My memory is fuzzy on this exactly, but I remember they definitely raised the issue)

The rest is history. The launch proceeded, and the O ring seals failed, and the boosters exploded. Update, thanks to u/Masshole_Mick for clarifying, it was the fuel tank that exploded, due to the leak from the booster O ring failure.

I remember sitting in grade school when the principal came over the school wide PA system and announced the tragedy. It was a national tragedy.

To expand on u/hvgotcodes explanation, the o-rings sealed a joint between two sections of one of the two solid rocket boosters. They were made of rubber and because of the cold temperatures the morning of the launch, the o-rings became less compressible so the joint was not sealed which allowed hot gas to escape which shortly after, ignited the contents of the big orange tank full of fuel (liquid hydrogen and oxygen).

So on the Space Shuttle the Solid Rocket Boosters (SRBs) go through thermal loads, and as a result they expand over the course of the flight. In order to keep them together while simultaneously allowing them to expand, the outer shell of the SRBs is actually a number of separate pieces, with O-rings at the joints made of Viton to allow them to expand and contract as needed over the launch sequence.

The problem was that the O-rings have a temperature range where they expand optimally, and the day of the launch the temperatures were very cold and below the optimal range of the Viton material. As a result, when the shuttle launched, the O-rings didn’t seat correctly into the wall of the right SRB. However, by happenstance, the aluminum oxides produced by combustion in the SRB itself sort of plugged the leak, allowing the initial stages of the launch to proceed normally until around a minute into the flight. At this point, high wind shear dislodged the oxide material, at which point a plume of hot exhaust gas started exiting the side of the right SRB, and was pointed straight at one of the struts holding the SRB to the rest of the shuttle, and also burning into the liquid hydrogen portion of the external fuel tank.

Around 72 seconds in, the strut failed, causing the load to shift in the external fuel tank and basically throwing it forwards, all of which caused the orbiter to twist off of it’s normal heading, and at close to Mach 2 the resulting aerodynamic forces tore the shuttle apart.

NASA absolutely knew of the potential for failure of the O-rings, and had been warned by the manufacturer’s engineers, but proceeded with the launch anyway.

The o-ring explanation is accurate as far as it goes, as it was the immediate cause of the shuttle’s destruction. However, the horizontal stacking scheme of the orbiter, external tank, and solid rocket boosters was the root cause of both the Challenger and Columbia disaster. Mounting the orbiter alongside the external tank and solid rocket boosters exposed the orbiter’s heat shield tiles to debris from the external tank. Since the external tank carried cryogenic fuels that were extremely cold and would require a lot of foam insulation, foam and ice shedding during launch was a predictable hazard to the fragile heat shield tiles. The horizontal stack also prevented any sort of abort scenario during the entire time the boosters were firing, and the boosters could not be extinguished once ignited. The lack of an abort system doomed the Challenger crew, and falling external tank debris doomed the Columbia. Every other human-rated launch system has used some sort of escape rocket system to save the crew at any time during launch.

Notably, SpaceX’s Starship also does not have an escape system. I won’t comment on the wisdom of this decision.

For a five-year old answer, it was very cold the morning of the launch which froze rubber seals. Just like your house gets drafty because of leaks in winter, the rocket developed leaks, and when rocket fire leaks out the side, things go boom. In a bad way.